Computably Enumerable Sets and Quasi-Reducibility

We consider the computably enumerable sets under the relation of Qreducibility. We first give several results comparing the upper semilattice of c.e. Q-degrees, RQ, ≤Q , under this reducibility with the more familiar structure of the c.e. Turing degrees. In our final section, we use coding methods to show that the elementary theory of RQ, ≤Q is undecidable.

• Type: Journal
• Year: 1998
• Where: APAL
• Authors: Rodney G. Downey, Geoffrey LaForte, André Nies
• Keywords: APAL 1998, Enumerable Sets, Familiar Structure, Upper Semilattice